Double-acting type slack adjuster for brakes



Dec. 18, 1956 B, H, BROWALL 2,774,449

DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES Flled Jan. 7, 1955 6 Sheets-Sheet 1 O a &

h w a INVENTOR BERT HENRY BROWALL Att i DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES INVENTOR YBERT HENRY BROWALL 4 mm Fifi-gs.

Dec. 18, 1956 B. H. BROWALL 2,774,449

DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES Flled Jan. '7, 1955 6 Sheets-Sheet 3 INVENTOR B HENRY BROWALL BY 71' PM Att s.

Dec. 18, 1956 DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES Filed Jan. 7

B. H. BROWALL 6 Sheets-Sheet 4 INVENTOR BERT HENRY BRO WA WM, +7 -MJ.

AttgS.

Dec. 18, 1.956 B. H. BROWALL 2,774,449

DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES 6 Sheets-Sheet 5 Flled Jan. 7, 1955 Dec. 18, 1956 B. H. BROWALL 2,774,449

DOUBLE-ACTING TYPE SLACK ADJUSTER FOR BRAKES Filed Jan. 7, 1955 6 Sheets-Sheet 6 INVNTOR BERT HENRY BROWALL Unite States Pflfgn DOUBLE-ACTING TYPE SLACK ADJUSTER FOP. fiRAKES Bert Henry Browall, Malmo, Sweden, assignor to Svenslra Aktiebolaget Bromsregulator, Malina, Sweden, a corporation of Sweden Application January 7, 1955, Serial No. 480,323

6 Claims. (Cl. 188196) My present invention relates to automatic slack adjusters for brakes for railway cars and the like, and the chief object thereof is to provide an improved automatic slack adjuster of the adjusting-screw type disclosed in my U. S. Patent No. 1,983,897, dated December ll, 1934.

The slack adjuster disclosed in my said U. S. Patent No. 1,983,897 serves its purpose efiiciently and reliably. Nevertheless, it suffers from some drawbacks in that the means for locking it against unintentional paying out of slack under the action of stresses arising at released brake when the car is submitted to shocks are associated with its actuating means, which are thus rendered more complicated and require rather precise dimensioning and mounting. Furthermore, a complete return of the foundation gear of the brake to the full release position after each application is necessary in order to render the locking means active. These several requirements will not always be satisfactorily fulfilled in practice. It is an objcct of my present invention to provide a double-acting slack adjuster of the adjusting-screw type disclosed in my said U. S. Patent No. 1,983,897, in which said drawbacks are eliminated.

Further objects of my present invention will be apparent from the following detailed description of two forms thereof, taken together with the accompanying drawings, in which:

Fig. 1 is a plan view illustrating the central part of a conventional American type of brake gear for freight cars and a preferred mounting therein of a double-acting slack adjuster embodying a form of my present invention, which is preferred especially for use in brake gears of this or any similar type. Fig. 2 is a detail plan view, partly in section, of this slack adjuster. Fig. 3 is a perspective view of a detail, and Fig. 4 is a fragmental view of this detail, seen from above in Fig. 3, and a section of another detail. Figs. 5, 6, 7 and 8 illustrate by views similar to those of Figs. 1, 2, 3 and 4, respectively, a brake gear of a conventional European type and a double-acting slack adjuster embodying another form of my present invention.

While the automatic slack adjuster of my U. S. Patent No. 1,983,897 in the form described and illustrated therein performs its take-up motion during release of the brake, it might also be constructed so as to perform its take-up motion during application of the brake, which may be preferable, especially where the power available in the foundation rigging of the brake for returning it into normal position during release of the brake is small. The power available in the foundation rigging during application of the brake is always in abundant excess of the part thereof that is consumed by the double-acting slack adjuster for efiecting its take-up motion. This consideration also applies to the double-acting slack adjuster of my present invention, and in the form thereof illustrated in Figs. 1 through 4 of the accompanying drawings it performs its take-up motion during application of the brake, while the double-acting slack adjuster in the form of my present invention shown in Figs. 5 through 8 performs its take-up motion during release of the brake. Referring to- Fig. 1 of the accompanying drawings, the type of railway car brake system shown comprises the brake cylinder 1, the cylinder and floating brake levers 2 and 3, respectively, and the pull rods 4 and 5 which connect to the said levers 2 and 3 the levers and beams (not shown) carrying brake shoes for coaction with the wheels of the car. The levers 2 and 3 are interconnected by a pull rod 6, and the slack adjuster forms at least a portion of this rod; but as will be apparent to those skilled in the art the slack adjuster may be mounted at any other suitable place in the brake rigging, and it may be utilized equally well in. other types of brake riggings, including brake riggings of the variable leverage type.

Referring to Fig. 2, the slack adjuster comprises a non-rotatable head in the form of a jaw 8 having an extension sleeve 9 secured thereto, a non-rotatable adjusting screw 10, and a rotatable section interconnecting said non-rotatable head 8 and adjusting screw 10 and including an adjusting nut 11 engaging the adjusting screw 11}, so that by rotation of the adjusting nut 11 on the adjusting screw 10 in one direction or the other the length of the brake rod (6 in Fig. 1) formed by the slack adjuster is increased or reduced for increasing or reducing the slack which consists essentially of the clearances between the brake shoes and the wheels of the car at fully released brake. Besides the adjusting nut 11, to which is aflixed a tubular sleeve 11a extending over the spindle for protecting the thread from dirt and damage, the said rotatable sectioncomprises a retaining ring 12 and two hollow rod parts 13 and 14 interconnecting the retaining ring 12 and the nut 11. A friction clutch sleeve 15 is aifixed to and unites the adjacent ends of the rod parts 13, 14. A coiled spring 16 is interposed between the retaining ring 12 and a friction clutch ring 17, which clutch ring coacts with the clutch sleeve 15, and an antifriction thrust ball bearing 18 is inserted between the said clutch ring 17 and theadjacent end of the spring 16. The sleeve 9 and the clutch members 15 and 17 are surrounded by a rotatable mechanism casing comprising two interconnected parts 19 and 20, the former of which is provided with a crank arm 21 for connecting the said mechanism casing to the actuating means of the slack adjuster in a manner to be described later. The rotatable mechanism casing 19, 20 and the clutch ring 17 are interconnected by means of a one way clutch preferably in the form of a coiled clutch spring 22 which is fitted to aligned internal surfaces on the members 17 and 19. This one way clutch is designed so as to take the clutch ring 17 along in any rotation of the mechanism casing 19, 20 in the direction in which the nut 11 has to be totated on the screw 10 for reducing the slack of the brake. The sleeve 9 is provided with an external screw thread 23 cooperating with an internal screw thread 24, which latter is not provided on the mechanism casing 19, as in my U. S. Patent No. 1,983,897, but instead is provided on a separately rotatable axially displaceable ring 43 (shown in detail in Figs. 3 and 4) on the sleeve 9 within the mechanism casing 19, 20. The camming threads 23 and 24 are preferably double threads and they are in the same direction as the coacting threads of the screw 10 and the nut 11, which latter are non-selflocking and preferably right handed multiple threads. The retaining ring 12 has a limited axial play in relation to the sleeve 9, and this sleeve and the retaining ring 12 are provided with cooperating conical abutment and friction clutch faces 9a and 12a, respectively. There is also a limited axial play between the threads 23 and 24 on the sleeve 9 and the ring 43, respectively. In an internal annular groove 47 in the ring 43 there is inserted a ring 48 of rubber or any other suitable material to produce a limited frictional resistance to movement of the ring-43 on the sleeve 9. In its end facing the jaw 8, the ring 43 '(see Figs; 3 and 4) is provided with recesses'44 each receiving a projection 45 onthe casing 19. The width of the recesses 44 is considerably greater than that of the projections 45 in order to provide for a limited angular play of the casing 19 in relation to the ring 43, the limits of this angular play being defined by the projections 45 contacting one or the other of the facing sides 44a, 44b of the respective recesses 44. The bottom of the'recesses 44 is-stepped to provide a ledge 46 to define a smaller depth of the recesses 44 for the projections 45- when the of the respective recesses provision of a spring 49 for thrusting theextension sleeve 9 of the head or jaw 8 as far as possible into the mechanism casing 19, 20. In the forms of the invention shown, this spring 49 is inserted between two supports 50 and 52 on the end portion of the extension sleeve 9'remote from the jaw 8. The support 50 preferably consists of a resilient slotted Washer inserted in an annular groove 51 in the extension sleeve 9adjacent the inner end thereof, while the support 52 consists of a ring which is axially movable on the extension sleeve 9 and supported against the force of the spring 49 by a number of pegs 53 provided on a ring 55 and projecting radially therefrom through a corresponding number of longitudinal slots 54 'in'the extension sleeve 9. The ring 55 is slidable and is much less than the strength of the spring 16, for instance only 10 percent thereof, but is suificient for normally thrusting the extension sleeve 9 with its end face 59 into contact with the clutch ring 17. With the extension sleeve 9 in its normal position at released brake'as shown in Fig. 2, the ledge in the recesses 44 in the ring 43, at all possible angular positions thereof -in relation to the extension sle'eve'9 is more remote from the jaw 8 than is the end of the projections 45 facing the bottom of the recesses 44, because the ring 43, due to its friction element 48, will be carried along in'the movement of the extension sleeve 9 when this is being thrust into its normal position.

With the slack adjuster in starting position at released brake, the spring 49 also fulfills the task of creating, by reason of the friction it produces between the end face 59 of the non-rotatable extension sleeve 9 and the clutch ring 17, a certain frictional resistance against rotation of the rotatable parts 11, 12, 13, 14 of the brake rod formed by the slack adjuster, in addition to said parts 11, 12, 13, 14 being frictionally clutched to the clutch ring 17 through the clutch sleeve 15.

Referring again to Fig. 1; the actuating means of the automatic slack adjuster comprises a bell crank lever fulcrummed on-the head pin 26 of the brake piston rod 27, one arm of the bell crank lever 25 being connected with the crank arm 21 on the mechanism casing 19, by

'a link rod 29, and the other arm of the bell crank lever 25 being connected by a link rod 32 to a fixed bracket 33 preferably attached to the brake cylinder 1. The arrangement is such that the mechanism casing 19, 20, as viewed from the jaw 8, will be turned clockwise during application and anticlockwise during release, of the brake through'an angle which at a maximum brake piston travel in the cylinder would reach a value preferably of the order of 90 and preferably with one half thereof on eachside of the vertical through the axis of the brake rod formed by the slack adjuster.

the coacting faces 9a and 12a of the extension sleeve-9 and the retaining ring 12, respectively; With the slack adjuster in this condition, should a shock or the like create a pulling force in the brake ro'd formed by the slack adjuster, nothing will occur other than that the a spring 49 may yield to the force and thusperrnit the projections to move further into the recesses 44 without reaching the bottoms thereof, so that the faces 12a and 9a of the retaining ring 12 and the extension sleeve 9, respectively, will abut one 'another'to prevent'unintentional rotation of the rotatable parts 11, 12, .13, 14 of the slack adjuster under the action of the shock. It is to be noted that this automatic locking of the'slack adjuster against unintentional adjusting movements under.

the action of shocks orthe like can take place. with the foundation rigging in any possible position 'at'rele'ased brakes even if the return of the foundation rigging into normal position at'the release of the brake was not complete, for instancebecause of being obstructed by; the usual hand brake, having been left in an incompletely released position. a

The operation of the automatic slack adjuster in the described form thereof shown in Figs. 1 through 4 is as follows: i i Y 7 At an application of the brake, the actuating means, including the bell crank lever 25 and the link rod 29, im-

mediately begin to turn the mechanism casing 19, 211' of the slack adjuster in a clockwise direction as' viewed from the jaw 8. This turning of the mechanism casing 19, '20 first shifts the position of the projections"45' V in the recesses 44 in the ring 43 from contact with the side'44a into contact with the side 4417 (see Fig. 4), and during the continued turning of the-mechanism casing, the projections 45 carry the ring 43 and its thread 24 along in the movement against the small frictional resistance exerted by the friction element 48. The clutch ring 17 is carried along in the movement of the mecha-, nism casing by the clutch spring 22 and moves, in turn,

'my means of the coactingclutchsleeve 15, the rotatable parts 11, 12, 13, 14, 16, 18, 56, 57, 58 against the resistance thereto caused by friction between the clutch ring 17 and the end face 59 of the extension sleeve 9 and between the flange 57 and the ring 55. By this movement the nut 11 is screwed on the non-rotatable screw 10 in the direction to reduce the length of the brake pull rod 6 formed by the slack adjuster, that is, in the direction to reduce the brake slack. a

If the brake slack istoo small, the brake shoes will contact the wheels of the car after a shorter outward movement of the brake piston during application of the brake than that corresponding to acorrect value'of the brake slack. Until braking stress arises in the brake rigging during the application stroke of the brake, the

'screw 10 is moved along in the brake application movement by-the jaw 8 through the parts 9, 50, 49, 52, 53, 55, 57, 56, 58, 18,16, 12, 13, 15, 14,11. Whenever a resistance occurs during the brake application movement which can be overcome only by power in excess of that of the spring 49,-this spring will yield' and permit the ledges 46 in the recesses 44 to abut the endsof the projections 45 facing the ledges 46,'and the camming threads 23, 24 willthen be pushed into contact witheach other. 'The excess power will then be transmitted from the jaw 8 through the parts 9, 23, 24, 43, 46, 45, 19, 20, 17, 58,

'18, 16, 12, 13, 15, 14, 11 to the screw 10. -Upon contact of the'brake shoes with the wheels, braking stress develops in the brake rigging by pressure being built up in the brake cylinder 1, and the power transmitted throughthe slack adjuster increases. Just as in the slack adjuster of my U. S. Patent No. 1,983,897, the increasing braking stress in the brake pull rod formed by the slack adjuster causes, due to the non-selflocking threads of the screw and the nut 11, an increasing torque on the nut, tending to rotate it in the direction to increase the length of the brake pull ro'd formed by the slack adjuster, that is in the direction to increase the slack. At the same time the pressure between the friction clutch members and 17 decreases, and when the increasing torque on the nut 11 overcomes the decreasing friction between the members 15 and 17, the nut 11 will rotate, thereby increasing the length of the brake rod formed by the slack adjuster, and thus permitting the brake piston to move further outwards in the brake cylinder 1. This further outward movement of the brake piston causes the mechanism casing 19, and thereby the ring 43 to be turned further (still in the clockwise direction as viewed from the jaw 8) along the screw thread 23 on the extension sleeve 9, thereby allowing the sleeve 9 and the jaw S to move to the right in Fig. 2 in relation to the retaining ring 12. These movements continue until the face 9a on the extension sleeve 9 abuts the face 12:! on the retaining ring 12, and then the braking stress will be transmitted from the jaw 3 and its extension sleeve 9 directly to the retaining ring 12 and therefrom through the parts 13, 15, 14 and 11 to the screw 10. When abutting one another under the action of the braking stress, the faces 9a and 12a efiectively lock the rotatable parts 11, 14, 15, 13, 12 against rotation, so that during the continued braking operation, the brake rod formed by the slack adjuster will not change its length and thus will allow the braking pressure to be built up to its full value. During the last part of the turning of the mechanism casing 19, 21) after the nut 11 has been locked against rotation by the coacting faces 9a, 12a, the clutch ring 17 and the sleeve 56 are carried along in the movement, slipping in relation to the clutch sleeve 15 and the ring 55, respectively, While the ring 43 is turned further by its thread 24 along the thread 23 so that the pressure between the ledges 46 and the projections ceases.

At the release of the brake the mechanism casing 19, 20 is turned back again towards its normal position by the actuating means. During the first part of this movement the projections 45 shift their position in the recesses 44 from contact with the side 44b to contact with the side 4411, whereupon the ring 43 is carried along in the rotation of the mechanism casing 19, 2t and will be moved by its thread 24 along the thread 23 on the sleeve 9 to the right in Fig. 2 with the ledges 46 clear of the projections 45. The clutch spring 22 is inactive during the rotation of the mechanism casing 19, 20 back towards its normal position, and the rotatable parts of the brake rod formed by the slack adjuster are prevented from partaking in this rotation first by the engagement of the faces 9a, 12a with one another until the pulling force in the brake rod has diminished to a value lower than that to which the spring 49 yields, and then by the friction caused by the spring 49 between the end face 59 of the extension sleeve 9 and the clutch ring 17 and between the ring and the flange 57 on the sleeve 56. Consequently, when the brake has been released, the brake slack which was too small has been corrected so as to correspond to a correct length of the brake piston travel during a braking operation.

If the brake slack is too large, the brake shoes will not contact the wheels until the brake piston has moved a distance in excess of the normal application travel re quired for bringing the faces 9:: and 121 into engagement with one another. During the first part of the braking operation the slack adjuster again operates in the same manner as it did when the slack was too small, in that the projections 45 first shift their position in the recesses 44 into contact with the side 44b and then carry the ring 43 along in the rotation of the mechanism casing 19, 20.

"6 The rotatable parts of the brake rod formed by the slack adjuster are carried along in the rotation of the mechanism casing 19, 21 by the clutch spring 22 and the strong friction clutch 17, 15,- so the nut 11 will be screwed on the screw 10 in the direction to shorten the said brake rod until the brake shoes contact the wheels and braking stress begins to build up in the brake rigging. The rising braking stress pulls the sleeve 9 to the right in Fig. 2 under compression of the spring 49, and as the ring 43 has now been turned a greater angle than in the first case, the

camming threads will not be drawn into contact before the faces 9a and 12a are brought into engagement with one another and thereby lock the rotatable parts of the brake rod formed by the slack adjuster against further rotation. After that, the clutch ring 17 will have to slip in relation to the clutch sleeve 15 during any continued rotation of the mechanism casing 19, 26 by the actuating means. When, during the subsequent release of the brake, the mechanism casing 19, 20 is turned back again by the actuating means, the slack adjuster again operates in the same manner as when the slack was too small. Consequently, when the brake has been released, the shortening of the brake rod effected during the application of the brake is maintained, and thus the brake slack which was too large has been reduced. The slack adjuster will repeatedly operate in this manner to reduce the slack, when it is too large, during as many subsequent braking operations as may be required for restoring the slack to normal value.

Also, when the brake slack is the correct value, the slack adjuster operates in the manner already descnibed during the beginning of a brake application movement, in that the projections 45 first shift their position in the recesses 44 into contact with the side 44!) and then carry the rotatable parts of the brake rod formed by the slack adjuster along in the rotation of the mechanism casing 19, 20- so as to effect an initial take-up motion of the. slack adjuster with the result that the brake shoes will come into contact with the Wheels shortly before the face 9a engages the face 12a. Just before this engagement of the faces 9a and 12a with one another occurs, the beginning stress in the brake rod formed by the slack adjuster causes the latter to perform a small screwing out motion just sufficient for compensating the mentioned initial take-up motion. These screwing in and out motions of the slack adjuster during the application of the brake balance one another in a very sensitive manner, so that the slack adjuster will react even to a very small deviation of the brake slack from its correct value.

The form of the invention described with reference to Figs. 5 through'8 differs from the form shown in Figs. 1 through 4 only in the following respects: the slack adjuster forms the main brake pull rod 4, or a part thereof; the actuating means including the bell crank lever 25 and the link rod 29 connecting it to the crank arm 21 of the mechanism casing 19, 26 are arranged so as to turn the latter, as viewed from the head 8, in a counterclockwise direction during application and a clockwise direction during release of the brake; the camming threads 23 and 24 are lefthanded, while the coact-ing threads of the screw 10 and nut 11still are righth-anded; the recesses 44 in the ring 43 (see Figs. 7 and 8) are reversed (as compared with Figs. 3 and 4).

In operation, the form of Figs. 5 through 8 difiers from that of Figs. 1 through 4 only in the following respects: The screwing in motion of the slack adjuster takes place during release instead of during application of the brake. The clutch spring 22 is inactive during application of the brake so that the brake application movement does not encounter the resistance which in the form of Figs. 1 through 4 is caused by slipfriction between the clutch members 15 and 17. Instead, the clutch spring 22 is active during release of the brake so that at the start of the release movement of the brake and as long as a certain brake stress is still present, the clutch ring 17 slips in relation to the clutch sleeve 15 until the braking stress has the mechanism casing 19, 20 is rotated further by its' actuating means towards its normal position. This takeup motion has to" overcome the frictional resistances between the end face 59 andthe clutch ring17 and .be-I

tween the members 55 and 57. Though these resistances are not very large, they consumepart-of the power of the return spring 7, which is usual in brake gears of the type illustrated in Fig. 5, but not usual in brake gears of the type illustrated in Fig. 1. At the correct value of the brake slack, the take-up motion of the slack adjuster during the release of the brake for one braking operation is balanced by a corresponding s'crewing out motion of the slack adjuster during the application of the I brake for the nextbraking operation. I

WhatI claim and desire to secure by Letters Patent is:

V 1. An automatic slack adjuster of the character described for brakes on railway cars and the like, comprising a brake rod included in the brake rigging and'comprising a first non-rotatable part, a second non-rotatable part and an intermediate rotatable section having a non-selflocking screw connection with said second part of said brake rod and being rotatable in both directions for increasing and reducing, respectively, the slack and adapted tobe rotated in the direction for increasing the slack through the stress arising in said brake rod when braking, coacting clutch faces on said first part and said rotatable section of said brake rod forlocking said rotatable section against rotation under theiaction of stress in 'said brake rod, a rotatable 'member on said brake rod, actuating means connected to-the brake structure and adapted to rotate said rotatable member in one direction during application andin the other direction during release of the brake, clutch means between said rotatable member and said rotatable section ofsaid brake rod for clutching said rotatable section to said rotatable member during rotation thereof in the di-' rection in which said rotatablesection is to be rotated for reducing the slack, movable abutment mea nslon'said first part of said brake rod, abutment means on said for tatable member coacting with said movable abutment mean s on said firstpart of said brake rod and shiftable angularly in relation thereto intoone and the other of two J difierent positions by the beginning of the rotation of said rotatable member occurring at application and release,

respectively, of the brake, and ,said coacting abutment means on said first part of said brake rod and said rota-table member being adapted, when in said one of said two angularly difierent positions, in relation to one another, to prevent said clutch faces on said first part and said rotatable section of said brake rodirom engaging one an- I and, when in said other of said two angularly difie'rejnt positionsin relation to one another, topermit s aid clutch'--" faces to engage one another at any point of rotation of 7 said rotatable member for locking said rotatable section againstrotation under the action of stress arising in said brake rod at released brake. a

2. An automatic slack adjuster as set forth inclaim in which said movable abutment means on said first part of said brake rod comprises an abutment member rotatable and axially movable on said first part of said brake rod and having-a threaded connection therewith comprising camming threads on said first part of sa id brake rod and said abutment member thereon, said; canimin I threads leavingbetween them an axial play. t a

V 3. An automatic slack adjuster as set forth in claim 2, in which said abutment means on said rotatable member'- comprises projections thereon, and in which said movable abutment means onsaid first part of said brake rod comprises a ring provided with the threads camming with the threads on'saidfir'st part of said brake rod, said ring being provided in one of its ends facing said projections with recesses receiving said projections and having stepped bottoms for coaction with them and permitting'displ-acement of-said projections into one and the other oftwo difierent angular positions of said'rotatablemember in relation to said ring by the beginning of the rotationof said rotatable member occurring during application and release, respectively, of the brake, and the stepped bottoms of said recesses providing a smaller axial play between them and said projections when said rotatable member is in said one than when it is in said other. of said two 'ditferent angular positions in relation to said ring.

4; An automatic slack adjuster as set forth in claim 3, V

inwhich a means exerting a limited frictional resistance to motion of said ring on said-first part of said brake rod is provided between the two;

5. Ant-automatic slack adjusteras set forth in claim 1, in which said rotatable member comprises a casing en closingsaid clutch means and said abutrnent'mean's, and in which saidjfir'st part of said brakegrod'comprises a jaw :having'i an" extension sleeve inscrted:-into said casing extension sleeve for thrusting the latter as far as possible tionally engages said intermediate rotatable member under 7 the action of said spring means as long as said spring means is not overcome by braking tension; 7

J No references cited;

forth in claim 

